I paid for it recently. So far it's been a mixed bag for me. The core works as intended, but little annoyances can add up.
I love that the design is small and light, but almost none of the languages is use are supported by Pygments for highlighting so someone browsing the code may find it off putting (GitLab I can use gitattributes to select a different but compatible Rouge highlighter). I like that NixOS is a first-class compatible image, but GitLab offered more in build options (run certain tasks only on tags, run this job on a cron, etc.). I love that I can push any markup I want to the ‘README’ of a project, but I wouldn't have to if Markdown wasn't the only option (MD's so limiting without admonitions, definition lists, block titles, ToC, etc.). Project discovery has a lot to be desired, but at least it doesn’t have gamification like “stargazers”.
